The chief executive of G4S has insisted his company will still claim its £57 million management fee for security at the Olympic Games, even though the company has presided over a “humiliating shambles”.

Nick Buckles faced repeated criticism from a committee of MPs as he struggled to explain how the company had failed to fulfil its contractual obligations to provide more than 10,000 security guards for the Olympic Games.

That failure has forced ministers to assign thousands of soldiers and police officers to basic security duties. Mr Buckles told the Commons home affairs committee that his firm would meet all the Government’s additional costs for those deployments, and was prepared to fund bonuses for troops assigned to Olympic duties if commanders thought it appropriate.

However, he made clear that he believed his firm was still entitled to its fee for managing the security arrangements for the Games. G4S holds a £284 million contract to provide security staff for the Games, which includes a £57 million “management fee”. Challenged to waive that fee, Mr Buckles insisted it should still be paid.

“We’ve managed the contract and we’ve had management on the ground for two years,” he said. “We still expect to deliver a significant number of staff.” Keith Vaz, the Labour chairman of the committee, told Mr Buckles his stance on the fee was “astonishing”.

That exchange followed questioning in which Mr Buckles offered an abject assessment of his company’s performance over the Games. When it was put to Mr Buckles that the affair had become a “humiliating shambles,” he replied: “I cannot disagree with you.”

The chief executive also faced personal embarrassment during his 90-minute appearance, frequently appearing hesitant or uncertain about details of the security operation. At one point, Mr Buckles said he was unable to say if his staff spoke “fluent English” because “I don’t know what fluent English is”.

G4S employs more than 600,000 people worldwide, and Mr Buckles insisted that the £284 million contract was “financially not a huge issue” for his firm.Instead of hoping to make money, he said, the company bid for the Olympic work to enhance its global image.

Instead, the debacle has become a worldwide embarrassment for the firm, whose shares have fallen by almost a fifth since its Olympic troubles were revealed last week. Mr Buckles admitted the affair had left his company’s reputation “in tatters”.

As a result of the London experience, G4S will now not bid for security work at the 2014 football world cup or the 2016 Olympics.

Mr Buckles told the MPs he was “deeply sorry” for the company’s performance, but rejected their suggestions that he should resign over the affair.

He said: “It’s not about me; it’s about delivering the contract. I’m the right person to ensure that happens.”